Dataset Information

Maternal Weight Gain During Pregnancy: Comparing Methods to Address Bias Due to Length of Gestation in Epidemiological Studies.

ABSTRACT: BACKGROUND:Studies examining total gestational weight gain (GWG) and outcomes associated with gestational age (GA) are potentially biased. The z-score has been proposed to mitigate this bias. We evaluated a regression-based adjustment for GA to remove the correlation between GWG and GA, and compared it to published weight-gain-for-gestational-age z-scores when applied to a study sample with different underlying population characteristics. METHODS:Using 65 643 singleton deliveries to normal weight women at 12 US clinical sites, we simulated a null association between GWG and neonatal mortality. Logistic regression was used to estimate approximate relative risks (RR) of neonatal mortality associated with GWG, unadjusted and adjusted for GA, and the z-score, overall and within study sites. Average RRs across 5000 replicates were calculated with 95% coverage probability to indicate model bias and precision, where 95% is nominal. RESULTS:Under a simulated null association, total GWG resulted in a biased mortality estimate (RR = 0.87; coverage = 0%); estimates adjusted for GA were unbiased (RR = 1.00; coverage = 94%). Quintile-specific RRs ranged from 0.97-1.03. Similar results were observed for site-specific analyses. The overall z-score RR was 0.97 (84% coverage) with quintile-specific RRs ranging from 0.64-0.90. Estimates were close to 1.0 at most sites, with coverage from 70-94%. Sites 1 and 6 were biased with RRs of 0.66 and 1.43, respectively, and coverage of 70% and 80%. CONCLUSIONS:Adjusting for GA achieves unbiased estimates of the association between total GWG and neonatal mortality, providing an accessible alternative to the weight-gain-for-gestational-age z-scores without requiring assumptions concerning underlying population characteristics.

SUBMITTER: Hinkle SN

PROVIDER: S-EPMC4818698 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature

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Maternal Weight Gain During Pregnancy: Comparing Methods to Address Bias Due to Length of Gestation in Epidemiological Studies.

Hinkle Stefanie N SN Mitchell Emily M EM Grantz Katherine L KL Ye Aijun A Schisterman Enrique F EF

Paediatric and perinatal epidemiology 20160224 3

<h4>Background</h4>Studies examining total gestational weight gain (GWG) and outcomes associated with gestational age (GA) are potentially biased. The z-score has been proposed to mitigate this bias. We evaluated a regression-based adjustment for GA to remove the correlation between GWG and GA, and compared it to published weight-gain-for-gestational-age z-scores when applied to a study sample with different underlying population characteristics.<h4>Methods</h4>Using 65 643 singleton deliveries ...[more]

PMID: 26916673

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Project description:BackgroundGestational weight gain (GWG) has important health implications for both the mother and offspring. Maternal diet during pregnancy may play an important role in achieving adequate GWG, although its precise role is unclear.ObjectivesAssociations between maternal dietary components (fruits and vegetables, added sugar, percentage energy from fat, dairy) and GWG were examined in 327 pregnant women from the Archive for Research on Child Health cohort.MethodsSelf-reported usual dietary intake was assessed with validated dietary screening tools at the first prenatal visit. GWG was obtained from the birth certificate and was categorized as inadequate, adequate, or excessive according to the Institute of Medicine recommendations. Associations between dietary components and GWG were assessed using multivariable regression models, stratified by maternal prepregnancy BMI category.ResultsOnly 31.5% of women had adequate GWG, with 24.8% gaining insufficient weight and 43.7% gaining excessively. Women who consumed more fruits and vegetables were suggestively less likely to have excessive GWG (OR: 0.86; 95% CI: 0.75, 1.00) in the minimally adjusted model, but the association became nonsignificant after adjusting for covariates (OR: 0.89; 95% CI: 0.77, 1.03). In stratified models, higher fruit and vegetable intake was linked to lower likelihood of excessive GWG among women with obesity (OR: 0.77; 95% CI: 0.60, 0.97), whereas higher added sugar intake was linked to a slight reduction in likelihood of excessive GWG (OR: 0.91; 95% CI: 0.84, 0.99) among women with a prepregnancy BMI in the normal range. Other dietary components were not significantly associated with GWG.ConclusionsThese results suggest that consuming fruits and vegetables during pregnancy may reduce risk of excessive GWG among women with obesity. With the rising prevalence of obesity among women of reproductive age, interventions to increase fruit and vegetable intake during pregnancy may have broad public health impact by improving maternal and child health outcomes.

Project description:Importance:Gestational weight gain is a determinant of infant birth weight, but it is unclear whether its timing in pregnancy may hold implications in this regard. Previous studies have yielded conflicting findings on the association of maternal weight gain in early pregnancy with birth weight. However, as these studies have typically recruited women during the first trimester, they are inherently limited by a reliance on self-reported pregravid weight. Objective:To evaluate the associations of directly measured maternal pregravid weight and the timing of subsequent weight gain across pregnancy with infant birth weight. Design, Setting, and Participants:In this prospective, preconception, observational cohort study, 1164 newly married women in Liuyang, China, underwent pregravid evaluation at a median of 19.9 weeks before a singleton pregnancy during which they underwent serial weight measurements. The study was conducted from February 1, 2009, to November 4, 2015. Data analysis was performed between September 1, 2016, and May 6, 2017. Exposure:Maternal weight gain was calculated for the following 10 gestational intervals: from pregravid to less than 14, 14 to 18, 19 to 23, 24 to 28, 29 to 30, 31 to 32, 33 to 34, 35 to 36, 37 to 38, and 39 to 40 weeks. Main Outcomes and Measures:Associations of pregravid weight and weight gain within each of the 10 gestational intervals with the outcome of infant birth weight. Results:The mean (SD) age of the 1164 women included in the study was 25.3 (3.1) years. Pregravid weight was consistently associated with infant birth weight. However, among the 10 gestational intervals, only weight gain from pregravid to 14 weeks and from 14 to 18 weeks was associated with birth weight. Birth weight increased by 13.6 g/kg (95% CI, 3.2-24.1 g/kg) of maternal weight gain from pregravid to 14 weeks and by 26.1 g/kg (95% CI, 3.8-48.4 g/kg) of maternal weight gain from 14 to 18 weeks. Conclusion and Relevance:Maternal weight only in the first half of gestation is a determinant of infant birth weight. Before pregnancy and early gestation may be a critical window for intervention to affect subsequent birth weight.

Dataset Information

Maternal Weight Gain During Pregnancy: Comparing Methods to Address Bias Due to Length of Gestation in Epidemiological Studies.

Publications

Maternal Weight Gain During Pregnancy: Comparing Methods to Address Bias Due to Length of Gestation in Epidemiological Studies.

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